Ignition device for use with safety fuses or the like



Aprii 22, 1941. D. E. PEARSALL grim. 2,239,051

N DEVICE FOR USE WITH SAFETY FUSES OR THE LIKE IGNITIO Filed March 16, 1939 Patented Apr. 22, 1941 UNHTED STATES err-ice IGNITION DEVICE FOR USE WITH SAFETY FUSES OR- THE LIKE Application March 16, 1939, Serial No. 262,144

5 Claims.

Our presentinvention relates to a cord-like ignition device for use in initiating a number of explosive charges, as in mining, military uses and in pyrotechnic displays, and aims to provide certain improvements therein.

The primary object of our invention is, to provide such a device as will insure in mine blasting a safe and simple method of igniting a number of safety fuses used in a blasting round by the single application of a flame, glow or other source of heat to a given point which may be located at any desired distance from the actual mine fuses and thereby afford the shot-flrer improved conditions of safety. Among the further objects of the invention the following may be enumerated: To provide an ignition device whereby a number of holes of a blasting round may be fired in any desired rotation without trimming the fuse ends, or whereby any number of holes can be caused to flre simultaneously 'while the remaining holes may be fired in any desired order.

Prior to our invention it has never been found practicable to ignite rounds of safety fuse from a distance by means of an ignition device because of the inability to control the intensity of the flame and the burning speed of such device. Neither has it been possible to make such device sufficiently flexible, settable and moisture-proof to permit its use in damp places.

Moreover, all prior devices with which we are familiar were consumed in burning so that they would not remain supported in their original position, and in consequence would fall and dis- ..charge incandescent sparks or flame onto other parts of the ignition device, or onto-the safety fuses so as to destroy the rotational order of the round and create other serious hazards.

The foregoing various objections and difficulties are overcome by our invention, which, in

its underlying concept, consists of a cord-like 'but will not disturb the position or arrangement of the supporting element which will remain firmly in place after the fire has passed, al-

though it may be partly demolished'by the force of the subsequent explosion.

The invention will be better understood from the detailed description which follows when considered in connection with the accompanying drawing wherein the single figure shows a fractional side elevation of an ignition device or cord embodying our invention, with parts thereof being broken away to better illustrate the constructional details thereof.

Referring to the drawing, the ignition device which is of cord-like appearance may be said to consist of a central flexible and settable wire or the like it having upon its surface an adhesive coating ll over which is countered or disposed in encompassing relation a plurality of strands of textile or like yarns l2. The central structure formed by the wire Ill and textile strands i2 provides a support or absorbent base for a powder train or coating 13. Over the powder train are disposed textiles It wound in contra-direction giving the appearance of a basket weave and providing substantially uniformly spaced exposed areas l5 of the powder train. The whole structure is then given a waterproof coating l6 of lacquer, wax or other suitable material.

Since the function of the ignition device is to continuously ignite safety fuses and similar burning media to'which it may be connected at any point along its length, it is important that the projected flame be continuous and of suf-' ficient intensity to satisfactorily ignite the fuses or the like. i

A preferred form of ignition device which we have found to give satisfactory results consists of a #25 gauge annealed, tinned steel wire countered with six strands of 15/4 ply cotton yarns. A thin coating of special adhesive is applied to the wire causing the yarns to cling thereto. .After drying, this core structure is then coated with a powder paste consisting of mealed black powder in a binder solution of nitrocellulose. By varying the amount of the ingredients in the powder base the rateof burn may be controlled between limits of approximately one foot in a second to one foot in twenty seconds. The protective covering of textiles consists of four pairs of 16/1 ply yarn applied in a counter-clockwise direction and four pairs of similar yarn applied in a clockwise direction. The waterproofing composition which is used for coating the assembly may be any desired wax composition.

An ignition device as described, when ignited without departing from ment capable of being formed in ty fuses or similar burning media to which it may be connected at any point along its length.

Although we have shown and described a preferred embodiment oi our invention, it will be appreciated that the supporting structure, as well 5 as the powder train media may be different from that hereinbefore specifically described. For example, in lieu of the central supporting wire, it is possible to use an asbestos cord or other noncombustible, settable material. Where an asbestos core is substituted for the wire it may also serve to replace the yarn countering l2 and the sizing II and provide a central supporting structure for the powder train. Also, in lieu of the black powder base specifically mentioned, the powder train may be made frompowders'of the thermite (non-gaseous) type. It will also be appreciated that the burning speed of the ignition device might be varied by twisting together two or more slower burning powder-coated media as well as by varying the powder paste compo sition and the character of the waterproofing composition with which the ignition device is coated.

It will thus be seen that while we have shown and described a preferred embodiment of our invention, the concept underlying the same is of such character and scope as to permit of variations in the specific construction disclosed, within the range of mechanical and engineering skill,

the spirit of the invention. I a

What we claim is: 1. An ignition device comprising a flexible eleany desired shape independently 01' any supports and remain so during and after burning, a core of rapidly combustible material supported by said flexible element and a covering for said core,- said covering providing substantially uniformly 40 spaced exposed areas of the core of rapidly combustible material, whereby said ignition device as it burns will project a regulated flame from its surface. I i

2. An ignition device comprising a flexible element capable of being formed in any desired shape independently of any supports and remain so during and after burning, countering yarns encompassing said flexible element, a rapidly combustible material supported by said countering yarns, a partial covering for the combustible material so applied as to leave substantially uniformly spaced exposed areas of the rapidly combustible material and a waterproof coating encompassing the assembly.

3. An ignition device comprising a central wire capable of being formed in any desired shape and so remain independently of the means by which it is supported, a coating of rapidly combustible material supported by said wire, and a covering for said structure, said covering providing substantially uniformly spaced exposed areas of the rapidly combustible material whereby the ignition device as it burns will project a regulated flame from its surface.

4. An ignition device comprising a central wire capable of being formed in any desired shape and so remain independently of the means by which it is supported, countering yarns encompassing said central wire, a coating of rapidly combustible material supported by said countered wire, and a covering for said structure, said covering providing substantially uniformly spaced exposed areas of the rapidly combustible material, whereby the ignitiondevice as it burns will project a regulated flame from its surface.

5. An ignition device comprising a flexible wire capable of being formed in any desired shape and so remain independently of the means by which, it is supported, countering yarns encompassing said wire, -a coating of rapidly combustible material consisting of mealed black powder with a binder agent supported by said countered wire, a textile covering for the powder coating so applied thereover as to leave exposed areas 01 the powder for controlling the size of the surface flame provided by the powder while burning, and a waterproof coating encompassing the assembly.

DAVID E. PEARSALL. J D. RICH. 

